Hydraulic cross-regenerative circuit



June 14, 1960 R. E. PFJTZENMEIER HYDRAULIC CROSS-REGENERATIVE CIRCUIT Filed June 13, 1958 W K A 30/ OR LO 0 VIII/ll; 6 I lg.

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FLOW CONTROL DEVICE FLUID SUPPLY SOURCE INVENTOR.

ROBERT E. PFITZENMEIER T Tnamavs June 14, 1960 R. E, PFITZENMEIER HYDRAULIC CROSS-REGENERATIVE CIRCUIT Filed June 13, 1958 2 Sheets-Sheet 2 FLOW CONTR DEVCE aossai' E. amnanmaam a mi" A oy vs United States Patent HYDRAULIC CROSS REGENERATIVE CIRCUIT Robert E. Pfitzenmeier, Fanwood, N.J., assignor of onefourth to Addison T. Smith, Maplewood, N J

Filed June 13, 1958, Ser. No. 741,945

13 Claims. (CI. 60-97) This invention relates in general to hydraulic control systems and more particularly to a hydraulic cross-regenerative circuit for connecting two or more cylinders together.

It is an object of the invention to provide dual hydraulic cylinders each having a blind end chamber and a rod end chamber, the rod end chamber of each cylinder being connected to the blind end chamber of the other cylinder by any fluid line.

Another object of the invention is to providedhree or more hydraulic cylinders each having a blind end chamber and a rod end chamber, with the rod end chamber of each cylinder being connected by a fluid line to the blind end chamber of only one other cylinder and with each blind end chamber being connected by a fluid line to the rod end chamber of only one other cylinder.

Another object of my invention, in a multiple hydraulic cylinder cross-regenerative circuit, is that the diflference in cylinder velocities due to dissimilar flows into and out of the hydraulic system is less than it would be in a normal regenerative circuit.

Another object of my invention, in a multiple hydraulic cylinder cross-regenerative circuit, is that the diflerence in pressure due to dissimilar work loads is less than it would be in a normal regenerative circuit.

Other objects and a better understanding of my invention may be had by referring to the following description and claims taken in conjunction with the accompanying drawings, in which:

Figure 1 shows a cross-regenerative dual cylinder hydraulic circuit in direct relation with a pump, a threeway valve, and a flow control device; and

Figure 2 shows a cross-regenerative hydraulic circuit connecting three hydraulic cylinders together.

With specific reference to Figure l of the drawings, a dual cylinder hydraulic cross-regenerative circuit is designated by the reference character 10. The circuit comprises generally dual hydraulic cylinders 12 and 13 often referred to as reciprocating differential motors, each being supplied with hydraulic fluid under pressure from a fluid supply source 15 and 16 and each being regulated by a three-way valve 18 and 19 and a flow control device 21 and 22. The three-way valves 18 and 19 regulate the direction of fluid flow and the flow control devices 21 and 22 determine the amount of flow into and out of the cylinders 12 and 13.

The fluid supply sources 15 and 16 may be standard pumps which pump fluid under pressure to the cylinders 12 and 13, respectively. Return flow conduits 42 and 43 connected to the fluid supply sources 15 and 16 and to the three-way valves 18 and 19, respectively, permit the returning fluid to flow back into the fluid supply sources 15 and 16. The fluid supply source 15 is connected to the cylinder 12 by a conduit 33 and the fluid supply source 16 is connected to the cylinder 13 by a conduit 34. It is understood .that the conduits 33 and 34 may be of any size and of any material available on the market today.

The cylinders 12 and 13 each have pistons 24 and 25,

2,940,262 Patented June 14, 1960 "ice respectively, mounted therein reciprocable intermediate their ends, which divide the cylinders into blind end chambers 40 and into rod end chambers 41, respectively. Connected to each piston 24 and 25 are piston rods 27 and 28, respectively. The piston rods 27 and 28 pass through the rod end chambers 41 of the cylinders 12 and 13 and extend externally thereof and engage movable work loads 30 and 31, respectively. It is understood that-if double rods are employed in each cylinder, the end of a double rod hydraulic cylinder with the smaller rod diameter will be also referred to as the blind end chamber of the cylinder. The movable Work loads some 31 may be parts to be moved on modern tool machines and automation equipment. The cylinders 12 and 13 connected by the cross-regenerative circuit 10 may also be used in industry in general for pushing, pulling, lifting, lowering, feeding, transferring, riveting, shearing and counterbalancing. i

The blind end chambers 40 of cylinders 12 and 13 have ports 45 therein to permit the passage of fluid "there through. The rod end chambers 41 of cylinders 12 and 13 also have ports 46 to permit the passage of fluid there: through. A conduit 37 is connected to port 45 of the blind end chamber 40 of the cylinder 12 and to the port 46 of the rod end chamber 41 of the cylinder 13. A conduit 36 is connected to the port 45 of the blind end chamber 40 of cylinder 13 and to the port 46 of the rod end chamber 41 of the cylinder 12. i

The dual cylinder hydraulic cross-regenerative circuit 10 has primarily two beneficial functions. The first function of the circuit 10 isto cause the difierence in cylinder velocities due to dissimilar fluid flows into or out of the system to be less than it would be in a normal regen erative circuit. The second function of the circuit is to cause the diflerence in pressures acting on the pistons 24 and 25 due to dissimilar work loads 30 and 31 to be less than it would be in a normal regenerative circuit.

The present invention of the hydraulic cross-regenera tive circuit 10 differs from the normal regenerative circuit in that the dual cylinders embodied in the normal regenerative circuit are not cross-connected'by conduits but the blind end chamber and the rod end chamber in each cylinder are connected by conduits to each other. Thus, on the upstroke of the piston, the fluid displaced. in the rod end chamber will flow back into the blind end chamber of the same cylinder. Thus, dual hydraulic cylinders in -a normal regenerative circuit are independent of each other.

One of the functions of the cross-regenerative circuit 10 is to cause the difference in cylinder velocities 'due to dissimilar flows into and out of the hydraulic system to be less than it would be in the normal regenerative circuit. The dissimilar flows in to or out of the system are mainly caused by differences in the flow control devices 21 and 22. It is diflicult to adjust (or manufacture.) one flow control device exactly the same 'asanother to permit exactly the same amount of fluid to flow through both of them. Thus, because it is difficult to adjust (or manufacture) the flow control devices 21 and 22 exactly the same and since cylinder velocity is directly'pro'p'or tional to fluid flow into or out of the system, it is highly desirable to have a circuit that will cause the pistons to move in as perfect synchronism as possible. It is understood -that the difference in dissimilar flows, due to the difliculty of adjusting ormanufacturing the flow control devices precisely, is very slight. For example, if 10 gallons per minute were required, one flow control device may pass 9.990 gallons per minute and the other flow control device may pass 10.010 gallons per minute. But even this minute diflerence may cause the pistons in a normal regenerative circuit, in a total travel length of 40 inches, to be off A of an inch or more. In close tolerance work,

as A of an inch or less. p

7 Q equals 2 plus (4 plus .5Q' I widetolerance ch 4 ofian inch is undesirable, It

7 will be shown that the cross-regenerative circuit 10'will' cause the cylinder velocitiesdue to dissimilar flows to be lessthan they would be in a" normal regeuerativecircuit and in a travel of 40-inches in the present'inventiomthe travel tolerance b etween'the two pistons may be as small 1 -Int he following flow formulas for cross-regenerative circuit, let Qequal the total flow into or out of the blind end of the cylinder; let B equal the cylinder rod chamber area divided'bythe cylinder blind chamber area; and let Qm equal the controlled rate of flow into or out of the system. I t;is.uuderstood in all the formulas given that the subscript represents cylinder 12 and the subscript represents cylinder 13. Thusthe flow formulas for cross-regenerative circuits are; a V r QfequalsQmi 1 1843 9, "(Equation lc cylinder 12 (Equation 2, Y cylinder 13) zit applying the two equations above mentioned, it is now possible to assign values to the letters in the formulas and prove that the difierence in cylinder velocities'in the cross-regenerative circuit due .to dissimilar flows is less it would be in the normal regenerative circuit.

of the cylinder. Thus, in the normal regenerative circuit, the piston in cylinder 13 will move eight units while the piston in cylinder 12 during the same interval of time will have moved .only fourrunits, a difference of four units. In the cross-regenerative circuit, the difference in unit travel of the pistons in cylinders 12 and 13, is only one and one-third (1 /3) units'. LThus; the pistons in the crossregenerative circuitwill be in .closer'synchronismthan in a normal'circu'it. It is understood that the unit s given hereinabove are hypothetical and for; illustration only, but the same flow formulas would apply .for any values given.

For a cross-regenerative circuit receiving 9,990 gallons per minute intothe'system at cylinder 12 and receiving 10.010 gallons per 1minute-intothesystem at cylinder 13, the fluid flow into the blind end chamber 40 at cylinder .12 will be 19.9933 gallons per minute and the fluid flow into the blind end chamber. 40 at cylinder 13 will be 20.0066 gallons per minute. Thus, the'ditference in fluid flow will be .0133 gallon per' minute, while therditference in fluid flow iu-the normal regenerative circuit will be'.04, thus three times as much as in the cross-regenerative circuit10.' V

In actual practice for typical installations, the stroke traveltolerance'or variancebetween the two pistons in identical and-the diameters of the rods are identical. 'Acthe overall eftect is that the cylinders 12 and 13 are matched. Assume that in cylinder 12, Qm equals 2 gallons per minute and B equals 5 Furtherass'ur'ne that in cylinder 13, Qm equals 4 gallons per minute and Bi equals 7 r It is understood that in this particular case for simplicity, the dissimilar flows are 4 gallons per minute and 2 gallons per minute, instead of 9.990 gallons per minute and 10.010 gallonsper minute. In actual practice, dissimilar flows from two different flow control devices a would never be two gallons per minute'iunlessit was def sirable to have the velocity of one piston to be faster than the other. The following is purely a hypothetical case.'

, With these values substituted in the Equations land 2, V

the equations become:

Q equals 2 plus .5 (Q -Q equals 5 plus.5(Q

The next step is to substitute the value of Equation 4 into (Equation '3, cylinder 12) (Equation 4, cylinder 13) Equation 3 and the equationlbecomes: V a 7 (Equation 5, cylinder '12).

' V V Removing the brackets, Equation 5 becomes: 7

Q equals 2 plus 2 plus .25Q

'(Equation 6,'cy linder 12) 7 Grouping likc terms, Equationo becomes:

per minuteandthat Q equals 4'gallons per minute; It

is' poted that the difference of flow into the blind end chamhers of, cylinders 12 and 13 in the cross-regenerativeicircuitis 1%, gallons per minute while the difierence minute. f

; Itis welliknown that cylinder velocity is directly. proj portional to flow into or out of the blindend chamber the cross-regenerative circuit v may be, for: example, as small as A of an inch, while in a normal regenerative circuit, the stroke travel variance under the same hereinabove-mentioned conditions may be, for example, as large as four inches or more. Thus,1 ih the;,cross regenerative. circuit, the difference in cylinder velocities due to dissimilar flows into and out of. the hydraulic system is less than it would be in a normal regenerative circuitg Another function of the cross-regenerative circuit 10 is to causethe diflerence in pressureacting jon'pistons 24 and 25 due to dissimilar work loads 30 and 31 tobe less than it would be in a normal regenerative circuit. Assume that the pistons in cylinders 12 and 13 in the normal regenerative circuit are on the upstroke andat a given instant the work load at cylinderpll is rapidly decreased. The piston 24 would tend to surge forward at that instant due to the pressure acting on a lighter. work load of the piston and thus the affected piston 2 4 would not be synchronous with the other piston 25. Thus dissimilar or changing Work loads, as Well as dissimilar flows, tend to cause a difierence in cylinder velocities. and fluid pressures. Assume that in the cross-regenerative circuit on the upstroke the work load'on cylinder 1271's rapidly decreased. Due to the pressure acting on the lighter work load of the afiected piston '24,;that piston'will surge forward. 7 Since the blind end chambers are connected to the rod end chambersof each cylinder, the pressure acting on one piston affects the pressure acting on theother piston.

Thus, when the pressure is changed in one chamber, the

.of, flow in the normal regenerative circuit is 4 gallons per;

pressure will also be changed 'in the other chamber'which is cross-connected thereto.= This tendency in'the crossregenerative circuit for the difference in pressure to become smaller in both pistons has a tendency to keep the two pistons in more perfect synchronism; and free from a jerking motion. In a typical'case, for example, assume 7 that two pistons are on the upstroke and at a given moment the work load'on one piston decreases from 2400 pounds to 1200 pounds." At that instant, the afiected piston may, for example, surge forward A of an inch. If the pistons .are not cross-connected, this change in the 7 work load at one piston willnot affect the other piston.

In the cross-regenerative circuit, a change'in pressure acting at one piston affects the pressure acting on the other piston'so thatthe pistons willkeep in closer synchronism than they would be-in a hormal regenerative circuit.

7 In the following pressure formulas let P equal pressure; let W equal the work load oriload reactionlforce,

including gravity; .let /l equal thecylindrical area of the blind end chambers 4 0glet C equal the ,cylindricatarea.

W equals A P minus C P and (Equation 9, cylinder 12) W equals A P minus C P (Equation 10, cylinder 13) Applying the two equations mentioned above, it is now possible to assign values to the letters in the equations and prove that ditference in pressures acting on the pistons 24 and 25 due to dissimilar work loads 30 and 31 is less than it would be in a normal regenerative circuit.

Again with specific reference to Figure l of the drawings, the following values are assigned to the difierent parts shown. In this particular case, the diameters of the cylinders and of the rods are identical. Accordingly, the overall efiect is that the cylinders 12 and 13 are matched. Assume that in cylinder 12, W equals 1200 pounds; A equals 5 square inches; and C equals 2.5 square inches. Further assume that in cylinder 13, W equals 2400 pounds; A equals 5 square inches; and C equals 2.5 square inches. It is understood that the figures given above are hypothetical and for illustration only. With these values substituted in the Equations 9 and 10 for finding pressure in the cross-regenerative circuit, the equation becomes:

1200 equals 5P minus 2.5P

(Equation 11, cylinder 12) 2400 equals 5P minus 2.51

(Equation 12, cylinder 13) Since P and P are the unknowns, Equations 11 and 12 are rewritten for P and P and become:

P equals (1200 plus 2.5P divided by 5 (Equation 13, cylinder 12) P equals (2400 plus 2.5P divided by 5 (Equation 14, cylinder 13) Dividing Equations 13 and 14 by 5, the Equations become:

P equals 240 plus 5P (Equation 15, cylinder 12) P equals 480 plus .5P (Equation 16, cylinder 13) Substituting the value for P into Equation 15, the equation becomes:

P equals 240 plus .S(480 plus .5P

(Equation 17, cylinder 12) Removing the brackets and grouping like terms, the Equation 17 becomes:

.7 SP equals 480 (Equation 18, cylinder 12) Thus, P equals 640 p.s.i. on cylinder 12. Substituting the value 640 in Equation 16:

Thus, P equals 800 p.s.i. on cylinder 13.

Using the same figures for finding pressure as employed hereinabove, it is found that P in the normal regenerative circuit equals 480 pounds per square inch and that P equals 960 pounds per square inch. It is noted that the difference of pressure acting on the pistons in the cross-regenerative circuit is 160 pounds per square inch, while the dilference of pressure acting on the pistons in the normal circuit is 480 pounds per square inch.

It is understood that the hereinabove values for P and P in the cross-regenerative and normal regenerative circuits are hypothetical and serve for illustration purposes only. But it is also understood that the abovementioned pressure formulas can be used for any values desired.

With specific reference to Figure 2 of the drawings, a multiple cylinder hydraulic cross-regenerative circuit is designated by the reference character 11. The circuit 11 comprises generally three hydraulic cylinders 12, 13 and 14, each being supplied with hydraulic fluid under pres- 6 sure from a fluid supply source 15, 16 and 17 and each being regulated by a three-way valve 18, 19 and 20 and a flow control device 21, 22 and 23. The three-way valves 18, 19 and 20 and the flow control devices 21, 22 and 23 have the same function as in the dual cylinder hydraulic cross-regenerative circuit 10. The fluid supply sources 15, 16 and 17 may be standard pumps and of the type described hereinabove and employed in the circuit shown in Figure l. The fluid supply sources 15, 16 and 17 are connected to the cylinders 12, 13 and 14 by means of conduits 33, 34 and 35, respectively, and the conduits may be of the type described hereinabove.

The cylinder 14 is the same type as cylinders 12 and 13 shown in Figure 1 and described hereinabove. Cylinder 14 has a piston 26 mounted therein reciprocable intermediate its end, which divides the cylinder into the blind end chamber 40 and the rod end chamber 41. Connected to the piston 26 is a piston rod .29 which passes through the rod end chamber 41 and extends externally thereof and engages a movable Work load 32. It is understood that the work load 32 may be the same as the loads 30 and 31.

The blind end chamber 40 and the rod end chamber 41 of the cylinder 14 have ports 45 and 46, respectively, to permit the passage of fluid therethrough. As shown specifically in Figure 2 of the drawings, the conduit 36 is connected to port 45 of the blind end chamber 40 of cylinder 13 and to port 46 of the rod end chamber 41 of cylinder 12. A conduit 38 is connected to port 45 of the blind end chamber 40 of cylinder 14 and to port 46 of the rod end chamber 41 of cylinder 13. A conduit 39 is connected to port 45 of the blind end chamber 40 of cylinder 12 and to port 46 of the rod end chamber 41 of cylinder 14. Thus, the rod end chamber 41 of each cylinder is connected by a conduit or fluid line to the blind end chamber 40 of only one other cylinder and the blind end chamber 40 is connected by a fluid line to the rod end chamber 41 of only one other cylinder.

The multiple cylinder hydraulic cross-regenerative cir cuit 11 has primarily the same functions as the dual cylinder hydraulic cross-regenerative circuit 10, which are described fully hereinabove. It is understood that more than three cylinders may be employed in the multi: ple cylinder hydraulic cross-regenerative circuit 11. Thus, any number of hydraulic cylinders may be employed in the circuit 11, as long as they are connected in the manner described.

The pistons upon completion of their power stroke may be returned to the beginning of a new stroke by the work actuating devices or by any external force. The return travel of the pistons would be controlled by synohronization of the system, the same as they are controlled on the power stroke. The flow control device and the cross-connected pistons would operate the same on the return stroke but in a reverse direction. Also, the pistons may be returned to the beginning of a new stroke by additional valving by drawing out the fluid in the cylinder chambers through external fluid circuits.

It is understood that the cylinders may be connected to a single fluid source, with a flow control device connected respectively in fluid circuit relation with each cylinder. In some installations, a single fluid source and a single flow control device connected respectively to all the cylinders may be used. Also in some installations the flow control device maybe entirely eliminated in the case of substantially uniform loading.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

, 'What is claimed is:;

g 1. A hydraiilic" cross-regenerative circuit adapted to be connec ed to a-fiuid supply source comprising, in com tbination, first and second cylinders, said first cylinder 'hav-' ing a first piston 'mountedthere in reciprocable intermediate its" ends, said first piston having first and second piston end areas dividing'sai'cl first cylinder into first and sec-' 7 ond chambers, afirs't piston rod connected to said first piston and extending from said second piston end a'rea th'ereof, said first piston rod passing through said second chamher in said first cylinder and extending externally thereof for performing work, said second cylinder having a second piston mounted therein reciprocable intermediate its ends, said second piston having first and second piston end areas dividing said second cylinder into first and second chambersfasecond piston rod connected to'said second piston andextendingt fr'om said second piston end area thereof, said second piston rod [passing lthrough said second chamberin said second cylinder and extending externally thereof for performing work, said first piston t end areaof said first piston being larger than said second piston area thereof, said first piston end area of said second pistonbeing larger thancsaid second piston area thereof, said first and second chambers in said first and ber of said secondrcylinder with said port means in said second chamber of saidpfirst cylinder. 7 a

2. A hydraulic cross-regenerative circuit adapted to be connected to a fluid supply sourcecomprising in combination, first and second cylinders, said first cylinder having piston means mounted therein reciproc'able intermediate its ends and: dividing said first cylinder into first and second chambers said second cylinder having piston means mounted therein reciprocable intermediate its ends and dividing said second cylinder into first and second chamhas, said piston means each having first and second end areas, said .first end area exposed to said first chamber and said second end area exposed to said second chamber, means connected to said second end area of each oftsaid piston means and extending externally of said respective cylinders for performing work, said second end area of said piston means being smaller than said first end area ofsaid piston means, said first and second chambers in' said first and secondcylinders having port means therein permittingthe passage of fluid therethrough, first conduit means'connecting said port means in said first chamber of said first cylinder with said fluid supply source, second condu'itimeans connecting'said port means in said first chamber of saidrsecond cylinder with said fluid supply source, third conduit'means connecting said port means in said first chamber of said first cylinder with said port 7 means in said secondchamber'of said second cylinder,

mediate its, ends andrdividing said first cylinder into first a r 8 r 7 smaller than the other said end area of said piston means, means connected to each of said piston means and ex tending externally of said respective 'cylinders;for performing work, said first and second chambers in said first and second cylinders having port means therein permitting the passageof fluid'therethro ugh, first conduit means connecting said port means in said first chamber of said first cylinder with said fluid supply source, second conduit means connecting said port means in said first chamber of said second cylinder with said fluid supply source, third conduit means connecting said port means in said first chamber'of said first cylinder with saidport means in said second chamber of said second cylinder, fourth conduit means connecting said'port means in said firs-tchamber of said second cylinderwith said port means in said second chamber of said first cylinder.

4. A'hydraulic cross-regenerative'cireuit adapted'to be connected to a fluid supply source comprising in combination, first and second cylinders, said first cylinder having a piston-mounted therein reciprocable intermediate its end and dividing said first cylinder into first and second chambers, said second cylinder having a piston mounted therein reciprocable intermediate its 'ends and dividing said second cylinderinto first and second chambers, said 7 piston means each having first and second end areas, said first end area exposed to said first chamber and said second end area exposed to said second chamber, a piston rod connected to said second end area of each'of said pistons and passing'through each of said second chambers in said first and second cylinders and extending externally thereof for performing work, said second end area of said .piston means being smaller than said first end area of said' piston means, said first andsecond chambers in said first and second cylinders having port means therehaving piston means mountedltherein reciprocable inter- I and second chambergsaid second cylinder having piston means mounted therein reciprocable intermediate its ends and dividing said second cylinder into first and second chambers,'said piston means each having first and second end areas, said first end area exposed to said first chamher and said second end area exposed to said second chamber, one of said end areas of said piston means being in permitting the passage of fluid therethrongh, first conduit means connecting said port means in said first cham-' ber of said first cylinder with said fluid supply source, second conduit means connecting said p r-tmeans'in said first chamber of said second cylinder with said fluid supply source, third conduit means connecting said port means in said first chamber of said first'cylinder with said port means in said second cylinder, fourth conduit means con necting said'port means 'in said first chamber of said second cylinder with saidport means in said second chamber of said first cylinder, first flow control means connected in fluid circuit relation with said first conduit means and intermediate said fluid source and said first chamber of said first cylinder, second flow control means connected 1n fluid circuit relation with said second conduit means and intermediate said fluid supply source and said first chamber of said second cylinder. T I 7 5. A hydraulic cross-regenerative circuit adapted to be connected to a fluid'supply source comprising in combinatron, first and second cylinders, said first cylinder having piston means mounted therein reciprocable'intermediate its ends and dividing said first cylinder into first and second chambers, said second cylinder having piston means mounted therein reciprocable'iutermediate its ends and dividing said second cylinder into first and second chambers, said piston means each having first and second end areas, said first end-area exposed to said first chamber and said second end area exposed to said second chamber, means connected to said second end area of each of said piston means and extending externally ofsaid respective cylinders for performing work, said second end area of said piston means being smaller than said first end'area of said piston'means, said first and second chambers in said first and second cylinders having port means therein permitting the passage of fluid therethrough, first conduit means connecting said port means in said first'chamber of said first cylinder with said fluid supply source, second conduit means connecting said'port means in said first chamber of said second cylinder with said fluid supply source, third conduit means connecting said portmeans means in said second chamber of said second cylinder, fourth conduit means connecting said port in said first chamber of said second cylinder with said port in said second chamber of said first cylinder, first flow control means connected in fluid circuit relation with said first conduit means and intermediate said fluid source and said first chamber of said first cylinder, second flow control means connected in fluid circuit relation with said second conduit means and intermediate said fluid supply source and said first chamber of said second cylinder.

6. A hydraulic cross-regenerative circuit adapted to be connected to a fluid supply source comprising in combination, first and second cylinders, said first cylinder having piston means mounted therein reciprocable intermediate its ends and dividing said first cylinder into first and second chambers, said second cylinder having piston means mounted therein reciprocable intermediate its ends and dividing said second cylinder into first and second chambers, said piston means having first and second end areas, said first end area exposed to said first chamber and said second end area exposed to said second chamber, one of said end areas of said piston means being smaller than the other said end area of said piston means, means connected to each of said piston means and extending externally of said respective cylinders for performing work, said first and second chambers in said first and second cylinders having port means therein permitting the passage of fluid therethrough, first conduit means connecting said port means in said first chamber of said first cylinder with said fluid supply source, second conduit means connecting said port means in said first chamber of said second cylinder with said fluid supply source, third conduit means connecting said port means in said first chamber of said first cylinder with said port means in said second chamber of said second cylinder, fourth conduit means connecting said port means in said first chamber of said second cylinder with said port means in said second chamber of said first cylinder, first flow control means connected in fluid circuit relation with said first conduit means and intermediate said fluid source and said first chamber of said first cylinder, second flow control means connected in fluid circuit relation with said second conduit means and intermediate said fluid supply source and said first chamber of said second cylinder.

7. A hydraulic cross-regenerative circuit adapted to be connected to a fluid supply source comprising in combination, first, second and third cylinders each having piston means mounted therein reciprocable intermediate its ends and dividing eachof said cylinders into first and second chambers, said piston means each having first and second end areas, and first end area exposed to said first chamber and said second end area exposed to said second chamber, rod means connected to said second end area of each of said piston means and passing respectively through said chambers in said first, second and third cylinders and extending externally thereof for performing work, said second end area of said piston means being smaller than said first end area of said piston means, said first and second chambers in said first, second and third cylinders having port means therein permitting the passage of fluid therethrough, first conduit means connecting said port means in said first chamber of said first cylinder with said fluid supply source, second conduit means connecting said port means in said first chamber of said secondcylinder with said fluid supply source, third conduit means connecting said port means in said first chamber of said third cylinder with said fluid supply source, fourth conduit means connecting said port means in said first chamber of said second cylinder with said port means .in said second chamber of said first cylinder, first conduit means connecting said port means in said first chamber of said third cylinder with said port means in said second chamber of said second cylinder, sixth conduit means connecting said port means in said first chamber of said first cylinder with said port means in said second chamber of said third cylinder.

8. A hydraulic cross-regenerative circuit adapted to be connected to a fluid supply source comprising in combination, first, second and third cylinders each having piston means mounted therein reciprocable intermediate its ends and dividing each of said cylinders into first and second chambers, said piston means each having first and second end areas, said first end area exposed to said first chamber and said second end area exposed to said second chamber, rod means connected to said second end area of each of said piston means and passing respectively through said chambers in said first, second and third cylinders and extending externally thereof for performing work, said second end area of said piston means being smaller than said first end area of said piston means, said first and second chambers in said first, second and third cylinders having port means therein permitting the passage of fluid therethrough, first conduit means connecting said port means in said first chamber of said first cylinder with said fluid supply source, second conduit means connecting said port means in said first chamber of said second cylinder with said fluid supply source, third conduit means connecting said port means in said first chamber of said third cylinder with said fluid supply source, fourth conduit means connecting said port means in said first chamber of said second cylinder with said port means in said second chamber of said first cylinder, fifth conduit means connecting said port means in said first chamber of said third cylinder with said port means in said second chamber of said second cylinder, sixth conduit means connecting said port means in said first chamber of said first cylinder with said port means in said second chamber of said third cylinder, first flow control means connected in fluid circuit relation with said first conduit means and intermediate said fluid source and said first chamber of said first cylinder, second flow control means connected in fluid circuit relation with said second conduit means and intermediate said fluid supply source and said first chamber of said second cylinder, third flow control means connected in fluid circuit relation with said third conduit means and intermediate said fluid supply source and said first chamber of said third cylinder.

9. A hydraulic cross-regenerative circuit adapted to be connected to a fluid supply source comprising in combination, a plurality of cylinders each having piston means mounted therein reciprocable intermediate its ends and dividing said cylinders into first and second chambers, said piston means each having first and second end areas, said first end areas exposed to said first chamber and said second end area exposed to said second chamber, means connected to said second end area of each of said pistons and extending externally of said respective cylinders for performing work, said second end area of said piston means being smaller than said first end area of said piston means, said first and second chambers in said cylinders having port means therein permitting the passage of fluid therethrough, conduit means connecting said port means in said first chamber of each said cylinders with said fluid supply source, conduit means interconnecting said port means in said second chamber of each of said cylinders respectively with said port means in said first chamber of each of said cylinders.

10. A hydraulic cross-regenerative circuit adapted to be connected to a fluid supply source comprising in combination, a plurality of cylinders each having piston means mounted therein reciprocable intermediate its ends and dividing said cylinders into first and second chambers, said piston means each having first and second end areas, said first end area exposed to said first chamber and said second end area exposed to said second chamber, means connected to said second end area of each of said pistons and extending externally of said respective cylinders for performing work, said second end area of said piston means being smaller than said first end area of said piston means, said first and second chambers in said cylinders having port means therein permitting the passage of 1'1 fluidtherethrough, first conduit'means connecting said port means in said'first chamber of each of said cylinders with-said fluid supply source, second conduit means interconnectingsaid port means in said second chamber of each of said cylinders respectively with said port means in said firstchamber of each of said cylinders, a plurality of flow control means respectively connected in fluid circuit relation with said first conduit means and intermediate said fluid supply source and said respective first chamber of said plurality of cylinders.

111, A hydraulic cross-regenerative circuit adapted to be 7 connected to a fluid supply source comprising in combination, a plurality of cylinders each having piston means mounted therein reciprocable intermediate its ends and dividing said cylinders into first and second chambers, said piston means each having first and second end areas, said first end area-exposed to said first chamber and said second end area exposed to said second chamber, means connected to said second end area of each of said pistons and extending externally of said respective cylinders for performing work, said second end area of said piston means being smaller than said first end area of said piston means, said first and second chambers in said cylinders having port means therein permitting the passage of fiuid there through, first conduit means connecting said port means in said first chamber of each of said cylinders with said fluid supply source, second conduit means interconnecting said port means in said second chamber of each of said cylinders respectively with said port means in' said first chamber of each of said cylinders, flow control means connected in fluid circuit relation with said first conduit means and intermediate said fluid supply source and said respective first chamber of said plurality of cylinders. 7

. 12. A hydraulic cross-regenerative circuit adapted to be connected to a fluid supply source comprising in combination, first and second cylinder means, said first cylinder means having piston means mounted therein and defining first andrsecond chambers, said second cylinder means having piston means mounted therein and defining first and second chambers, said piston means each having first and second end areas, said first end area exposed to said firstchamber. and said second end area exposed to said second chamber, means connected to said second end area of each of saidtpiston means and extending externally of said respective cylinder means for performing Work, said second end' area of said piston means being'smaller than said first end area of said piston means, said first and second chambers in-said first and swondcylinder means having port 7 means therein permitting the passage of fluid therethrough, first conduit means connecting said port means in said first chamber of said first cylinder t t 12 t r means with said; fluid supply source, se'cond'jconduit means connecting said port mean s' in said first chamber of said second cylinder means with :said fluid supply source, third condnitmeans connecting said port means in said first chamber of said first cylinder means'with said port means in said second chamber of said second cylinder means, fourth conduit means connecting said port means in said first chamberof said secondtcylinder means with 'said port means in said second chamber of saidtfirst cylinder means. a i a V t j 13. A hydraulic cross-regenerative circuit adapted to be connected to a fluid supply source comprisingin combination, first and second cylinder means, said first cylinder means having piston means mounted-thereidand defining first and seco nd chambers, said second cylinder means having piston means mounted therein and definingfirst and second chambers, saidpistonmeans eachlhaving first and second end areas, said first end areaiexposed to said first chamber and said second end area exposed to said second chamber, means connected .to said second'end area of each of, said piston means and extending externally of said respective cylinder means for performing work, said second end area of said piston means being smaller than said first end area of said piston'means, said first and second chambers in said first and second cylinder means having port means therein means permitting the passage of fluid th'erethrough, first conduit means connecting said port means in'said first chamber of said first cylinder means with said fluid supply source, second conduit means connecting said port means in said first chamber of said second cylinder means with said" fluid supply source, third conduit means connecting said port'means in said'first chamber of said first cylinder means withsaid port means in said second chamber of said second cylinder means, fourth conduit means connecting said port means in said first chamber of said second cylinder means with said port means in said second chamber of said first cylinder means, first flovv control means connected in fluid circuit relation with said first conduit means and intermediate said fluid source and said first chamber 'of said first cylinder means, second flowrconrtol means connected in fluid circuit relation with said second conduit means and intermediate said fluid supply source and said first chamber of said second cylinder means.

References Cited in t he file this patent" V UNITED STATES T 

